Botulinum toxin injections

Definition

Botulinum is a bacterium (Clostridium botulinum) that produces seven different toxins that can cause botulism and is also medically used to block muscle contractions.

Purpose

Botulinum toxin (Botox) injection is used in conditions of excessive and inappropriate muscle contraction, spasticity (persistent states of muscle contraction), sphincter contraction, eye-movement disorders, tics and tremors, and cosmetically to treat facial lines and wrinkles.


The U.S. Food and Drug Administration (FDA) approved Botox for treating excessive underarm sweating in 2004. Botox has also been used in the treatment of chronic muscle tension and migraine headaches. The relief is likely due to the decrease in localized muscle spasms, as no direct effect of Botox on the sensory nerves has been established. Botox may be prescribed off-label to help improve movement in children with cerebral palsy , but this use has not been approved by the FDA. The application of the therapy seems to be growing continuously beyond its more popularly known cosmetic uses.

Precautions

Botulinum toxin is produced from the bacterium that causes food poisoning in humans. High doses of the toxin can be fatal; however, doses administered therapeutically are so small that harmful effects are uncommon.



Description

The number of potential applications for botulinum toxin extends to every muscle group. The first therapeutic use of Botox was in the treatment of strabismus (eyes are unable to direct toward the same object) and since then it has been used to treat a variety of involuntary muscle contractions or disorders. Its cosmetic use is the result of treatment for facial spasms where smoothing of facial lines was reported by patients. In general, 90%of injections for facial spasms are resolved satisfactorily.

Toxin type A has a duration of effect that lasts approximately three months and is the therapeutic agent of choice for most conditions.

Preparation

The dosage of Botox must be monitored and adjusted, with multiple injections showing a lower incidence of complications versus administration by one larger dose.

Risks

In over 30 years of therapeutic use in humans, botulinum toxin has proven to be remarkably safe. Some difficulties associated with administration of toxin are that different patients may experience different effects at the same dose, patients new to the treatment may experience exaggerated effects at subsequent visits, and neighboring muscles may become activated at subsequent treatments. Patients should ask about their provider's experience with injecting Botox before receiving the procedure.

Additional side effects may include excessive muscle weakness at the injection site or adjacent muscles. These effects typically resolve quickly. Occasionally, patients report flu-like symptoms but they are usually self-limited.

A certain percentage of patients may also experience resistance to the toxin. The presence of circulating antibodies to the toxin is presumed to be the primary reason for resistance to Botox injections. Patients who have little reaction to Botox A may benefit from injections using one of the other six serotypes. Using the smallest effective dose limits the likelihood of immunoresistance in unresponsive patients.

Normal results

The anticipated outcome of Botox injections is relaxation of the target muscle tissue. The pharmacological effects of botulinum toxin are typically isolated to local areas and do not result in tissue destruction or prolonged paralysis. Varying the dose can deliver a precise amount of toxin to achieve graded degrees of paralysis for the desired level of response.

Abnormal results

Most side effects, such as weakness in the injected muscle or overall muscle soreness, will go away quickly. Some patients have received too much of the substance when having Botox for cosmetic purposes and have been unhappy with the results. Physicians and patients should discuss the procedure and the amount to be used. Many clinicians believe that it is best to err on the side of low dosage with a return trip for more, rather than too high a dosage that might result in unwanted cosmetic effects.